The present disclosure generally relates to acid-promoted treatment processes and, more specifically, to methods and systems incorporating particulates in acid-promoted treatment processes.
Treatment fluids can be used in a variety of subterranean treatment operations. Such treatment operations can include, without limitation, drilling operations, stimulation operations, production operations, remediation operations, sand control treatments, and the like. As used herein, the terms “treat,” “treatment,” “treating,” and grammatical equivalents thereof refer to any subterranean operation that uses a fluid in conjunction with achieving a desired function and/or for a desired purpose. Use of these terms does not imply any particular action by the treatment fluid or a component thereof, unless otherwise specified herein. More specific examples of illustrative treatment operations can include, for example, drilling operations, fracturing operations, gravel packing operations, acidizing operations, scale dissolution and removal operations, sand control operations, consolidation operations, and the like. Related types of treatment operations can also be conducted in pipelines or other conduits used in various industrial processes or that are in fluid communication with a subterranean formation.
Acidic treatment fluids are frequently used in the course of conducting various treatment operations. Illustrative uses of acidic treatment fluids during subterranean treatment operations include, for example, matrix acidizing of siliceous and/or non-siliceous formations, scale dissolution and removal operations, gel breaking, acid fracturing, and the like. When acidizing a non-siliceous material, such as a carbonate material, mineral acids such as hydrochloric acid may often be sufficient to affect dissolution. Organic acids such as formic acid or acetic acid may be used in a similar manner to hydrochloric acid when dissolving a non-siliceous material. Siliceous materials, in contrast, are only readily dissolvable using hydrofluoric acid, optionally in combination with other mineral acids or organic acids. Similar considerations apply when dissolving scales of various types.
During an acidizing or scale removal operation, an acid-reactive substance can be dissolved by one or more acids to expand existing flow pathways in a subterranean formation, to create new flow pathways in a subterranean formation, and/or to remove scale or acid-reactive precipitation damage. Similar benefits can be realized by treating a pipeline or other fluid conduit having an undesired acid-reactive substance therein. The acid-reactive substance can be part of the native formation matrix, form in the course of operating a wellbore (e.g., scale), or have been deliberately introduced into the wellbore (e.g., proppant or gravel particulates). In carbonate formations, for example, a carbonate mineral in the native formation matrix may be acidized in order to stimulate production.
Although carbonate minerals can be readily acidized with both mineral acids and organic acids, the acid's reactivity with carbonate minerals is often excessive and may lead to various undesirable effects. For example, excessively rapid reaction of a carbonate mineral with an acid can lead to bulk erosion, rather than the desired wormhole formation or the creation of other conductive channels in the formation matrix in order to increase permeability. As used herein, the term “wormhole” refers to a channel generated in the matrix of a subterranean formation that positively contributes to increased incremental permeability. Scaling may also become problematic when a carbonate mineral is inadvertently reacted with an acid and the solubility limit of dissolved metal cations is exceeded. Further, the reaction of mineral and organic acids with soft and friable matrices, particularly at elevated formation temperatures, can often occur too rapidly and lead to undesirable matrix deconsolidation.
Another problem associated with the rapid reaction of carbonate minerals and other acid-reactive substances is that the excessive acid reactivity can preclude placement of the acid in a location where its reactivity is more desired. For example, rapid spending of an acid in the near-wellbore region of a carbonate formation can preclude deeper penetration of the acid into the formation matrix to promote more effective stimulation. Techniques such as closed fracture acidizing, in which an acid is introduced into a fracture after it has been created but before it closes, may be used to address the penetration and acid reactivity issues. Both viscosified and non-viscosified acids may be used in this regard, but such techniques may not be applicable in carbonate formations also having significant quantities of quartz or aluminosilicates (15-65%). In order to achieve deeper acid penetration into the formation matrix, greater quantities of the acid may need to be used, which may be undesirable due to cost, safety, time and environmental considerations. Gel damage and/or acid-promoted damage to the near-wellbore region can also occur, which may necessitate further damage control and remediation operations, thereby adding additional cost and time delays. Costly diverting strategies and/or alternative treatment protocols not relying upon strong acids may sometimes be needed to avoid excessive reaction of a carbonate mineral with an acid in the near-wellbore region.